Missing $form_state[…][#value] in AJAX callback from <select> inside jquery UI $.dialog()

jqueryUI $.dialog() control is included on the form like this:

    '#attached' => array(
        'library' => array(
            array('system', 'ui.dialog'),
        ),
    )

I have an AJAX callback that returns an array of AJAX commands like this:

return array(
    '#type' => 'ajax',
    '#commands' => array(
        ajax_command_invoke("#dialog-container", 'remove'),
        ajax_command_replace("#dialog-container-holder", render($form['form']['dialog_container_holder'])),
        ajax_command_invoke("#dialog-container", 'dialog', array($dialog_config)),
    )
);

Part of the form, "#dialog-container" becomes a modal dialog and is filled with the proper form elements. The section of form inside the dialog includes a "select" that is handled by a different AJAX callback. The "select" triggers its callback but $form_state['triggering_element']['#value'] is empty - not updated with the select's value. How can I get $form_state to be updated correctly?

Note: In the callback that builds the dialog (above), I have to remove the previously-created "#dialog-container" or a duplicate section is inserted into the DOM and causes id conflict, etc. I tried to call $.dialog('destroy') on the old section (instead of remove) but that didn't prevent the duplication.